Stress relieving feature on strip welders

ABSTRACT

A method of seam welding wherein, first, portions of work parts are contacted by roller-welding electrodes which make a first pass to form a welded joint and, subsequently, roller electrodes, normally the welding electrodes, make a second pass over the welded joint at a controlled rate and at a reduced heat in order to heat the welded joint to within a predetermined temperature range below fusion temperature to stress relieve the welded joint prior to, or after, planishing thereof.

United States Patent Ellsworth E. Rhodes Bangor Township, Bay County,Mich. 765,154

Oct. 4, 1968 Feb. 16, 1971 By mesne assignments to Newcor, Inc. BayCity, Mich.

[72] Inventor [2i] App]. No. [22] Filed [45] Patented I73] Assignee [54]STRESS RELIEVING FEATURE ON STRIP WELDERS 11 Claims, 3 Drawing Figs.[52] US. Cl 219/83, 219/59, 219/67 [51] Int. Cl B23k 11/06, 323k 31/06[50] Field ofSearch 2l9/83,67,

59 Primary Examiner-J. V. Truhe Assistant ExaminerHugh D. JaegerAttorney-Woodhams, Blanchard and Flynn ABSTRACT: A method of scamwelding wherein, first, portions of work parts are contacted byroller-welding electrodes which make a first pass to form a welded jointand, subsequently, roller electrodes, normally the welding electrodes,make a second pass over the welded joint at a controlled rate and at areduced heat in order to heat the welded joint to within a predeterminedtemperature range below fusion temperature to stress relieve the weldedjoint prior to, or after, planishing thereof.

This invention relates to a-welding process and, more particularly,relates to a process of seam welding in which the welded joint is stressrelieved prior toplanishing or other subsequent treatment thereof.

BACKGROUND OF THE INVENTION In the known processes of seam welding, suchas in strip welders of the type disclosed in copending application Ser.No. 553,971, filed May 31, 1966, now U.S. Pat. No. 3,51 1,961, andassigned to the same assignee as the present invention, the welded jointformed is often brittle, particularly when the work parts are madeofmedium carbon and low alloy steels. As the strip, including the weldedjoint, is moved from the weld zone over rolls to other pats of themachine, a bending of the welded joint occurs. This may causethe-brittle welded joint to become fatigued'and may lead to eventualcracking thereof. Moreover, a. brittle welded joint more stronglyresists the subsequent planishing treatment-in which the welded joint iscold rolled in order to reduce the thickness thereof to as close aspossible to the parent metal thickness and to cold work the joint wasclose to the parent metal strength as possible.

Various attempts have been made in the past to anneal the welded jointto relieve the stresses'formed therein by welding. In some cases, thewelded joint has been heat treated by means of gas-burning flames, byinduction heating, or by other processes whereby the welded joint isheated to a predetermined temperature to relieve the stresses formed inthe welded joint. However, these prior types of procedures for stressrelieving the welding joint require additional, expensive equipment,they are expensive to carry out an it is difficult to accurately controlthe temperature to which the work parts are heated to effectsatisfactory annealing of the welded joint.

Accordingly, it is an object of this invention to provide a process forremoving or relieving the stresses in a welded joint to improve theductility of the welded joint by contacting the welded joint withwelding electrodes a second time and thereby supplying sufficient heatto the welded joint to effect a stress relieving thereof, but withouteffecting a second fusion.

It is a further object of this invention to provide a process, asaforesaid in which the welded joint is stress relieved after the weldhas been performed and .prior to planishing of the weld joint so thatthe planishing operation can be carried out effectively in order toreduce the thickness of the welded joint to as Is as possible to thethickness of a single one of the individual work parts and to cold worktheweld joint to increase the strength of the joint to as close to themetal strength work parts as possible.

It is a further object of this invention to provide a process, asaforesaid, in which the ductility of the weld joint is improved so thatthe welded joint can be moved from the weld zone to other parts of themachine over rollers without fatiguing and eventually cracking.

' It is a further object of the invention to provide a process, asaforesaid, which can be easily further extended without the need foradditional equipment to effect a stress-relieving procedure after theplanishing operation if desired.

It is a further object of this invention to apparent a method which canbe easily carried out this general type upon reading the seam weldingmachines.

Other objects and purposes of this invention will be apparent to personsacquainted with seam welding apparatus of this general type upon readingthe following specification and inspecting the accompanying drawings, inwhich:

FIG. I is a schematic illustration of a seam welding. apparatus forcarrying out the method of the invention;

FIG. 2 is a cross section of the work parts which have been joinedtogether by welding prior to planishing thereof;

FIG. 3 is a schematic illustration similar to a fragment of FIG. 1showing the welding electrodes making a second pass over the work partsfollowed by the gaging the work pans.

Certain terminology will be used in the following descriptive materialfor convenience in reference only and will not be limiting. The wordsup," down," right" and left will designate directions in the drawing towhich reference is made. The words in. and out will refer to directionstoward and away from respectively, the geometric center of the deviceand designated parts thereof. Said terminology will include the wordsabove specifically mentioned, derivatives thereof and words of similarimport.

SUMMARY OF THE INVENTION The objects and purposes of the invention aremet by providing a method in which after the welding operation, a pairof electrodes are moved along the welded joint under controlledconditions whereby the work parts are again heated to within apredetermined temperature range below the weldment required.Accordingly, the primary concept is to pass the same set of electrodestwice over the work parts, the first time performing a welding operationand the second time performing a stress-relieving operation. 1

DETAILED DESCRIPTION While the invention lies mainly in the method forstress-relieving a welded joint, it is believed that the method will bemore conveniently and readily understood by describing it in conjunctionwith an apparatus 10 by which it can be carried out. It is to beunderstood that the apparatus described hereinbelow for practicing themethod is illustrative only and is not intended to be limiting.

Referring now to FIG. I, a pair of work parts 11 and 12 are overlappedto define an elongated zone in which a seam weld is to be formed. Thework parts 11 and 12 may be, for example, the head end of an incomingstrip I (FIG. 2) and the tail end of an outgoing strip 0 and theapparatus 10 may be a strip end welding machine having a structuresimilar to that disclosed in the aforesaid copending application Ser.No. 553,971, tiled May 31, 1966. The work parts move in a directionperpendicular to the plane of the paper in FIG. I.

Vertically aligned welding roller electrodes 13 and 14 are positioned soas to engage opposite sides of the elongated weld zone X on the workparts 1-! and 12. In the particular embodiment shown, the upper weldingroll 13 is rotatably supported shaft 16 which is secured to a verticallyreciprocable rod [7 energized by a fluid pressure cylinder 18 secured toa movable carriage 19. The lower welding roller 14 is rotatablysupported on' a shaft 21 which in this embodiment is secured to avertically reciprocable rod 22 energized by a pressure fluid cylinder 23secured to another part of the carriage 19. In many instances, however,the mounting of one of the welding rollers 13 and 14 is fixed with onlythe other being'reciprocable. The carriage 19 is movable in a directiontransverse to the direction of travel of the work parts 11 and Handlengthwise along the weld zone X.

The roller electrodes 13 and 14 are connected in any convenient'mannerto the opposite terminals of a secondary winding 24 of a weldingtransfonner 26. The welding transformer is supplied in any convenientand conventional manner from a source of electrical energy 27 controlledby a control 28. The pressure fluid cylinders 18 and 23 are energized ina predetermined andadjustable pattern by the control 28 to therebyprovide acontrolled pressure by which the roller electrodes 13 and 14are urged against the work parts 11 and 12, and respectively.

planishing rollers also enpattern as hereinafter described.

Vertically aligned planishing rollers 29 and 31 engage opposite sidesof'the weld zone X and they are disposed in aligned relationship to thewelding electrodes 13 and 14. In the particular embodiment shown, theupper planishing roller 29 is rotatably supported on a shaft 32 securedto a vertically reciprocable rod. 33-of a pressure fluid cylinder 34,said cylinder being energized by the control 28 for controlled verticalmovement and pressure. The fluid pressure cylinder 34 is secured to thecarriage 19. The lower planishing roller 31 is rotatably supported on ashaft 36 secured in this embodiment to a vertically reciprocable rod 37of a fluid pressure cylinder 38, which latter is secured to the carriage19. The fluid pressure cylinder 38 is also energized by the control 28so that the planishing roller 31 can be movedvertically and the pressureexerted thereby on the weld zone X canv be controlled. However, as withthe welding roller, inf'm'any instances the mounting for one of theplanishing rollers 29 or 31 is f xed and only the other is reciprocable.l I t I a The carriage 19 is supported for movement by any convenientmeans such as rollers, oneof which is indicated by 39 in FIG. 1; Thecarriage 19 is secured to any means for effecting reciprocation thereof,in this-embodiment a screw 41 driven by motor 42,'said motor beingsecured to a stationary frame 43. The motor 42 is energized by thecontrol 28 to move the carriage 19 in the desired sequence. it isrecognized, of

course, that the control 28 can be of the manual variety but in thepreferred embodiment, the control 28 can be programmed so that theenergization of the cylinders 18, 23, 34 and 37 and the motor 42 willoccur automatically and is a synchronized OPERATION The method of theinvention will be described with reference to the operation of theapparatus. At the start, the carriage 19 and thereby the rollerelectrodes 13 and 14 will be in a position adjacent the left edge of thework parts 11 and 12 and said electrodes will be vertically spaced fromthe work parts. After the work parts are overlapped, the control 28 willthen energize the fluid pressure cylinders 18 and 23, assuming both areused, to cause a movement of the roller electrodes 13 and 14 intocontact with the work parts 11 and 12, respectively. The pressureapplied to the rollerelectrodes 13 and 14 will be sufficient to causethe work parts 11 and -12 to be urged tightly together so that acompleted electrical circuit will exist between the roller electrodes 13and 14,through the clamped work parts 11 .and 12. Simultaneouslytherewith, the control lesser pressure can be used, if desired. ln'themeantime, the 7 control 28 now' maintains the flow of current betweenthe electrodes 13 and 14 at a diminished value such that it will not besufficient to produce a welding heat or a second fusion .of I the weldseam. Rather the current should now be sufficient only to heat thewelded joint W to stress-relieving temperature, which for most steels isordinarily in the range of 800 to [200 F. Thus the heat produced willstress relieve welded joint W to eliminate or reduce the stressestherein and increase the ductility of the weld joint W. It will berecognized that, during the leftward movement of the'carriage 19, thespeed of movement of said carriage can be increased by the control 28and this can be used in lieu of, or in combination with, the reductionof the current output of transformer 26 to insure that the heat suppliedto the weld zone will be sufficient only for stress relieving the weldzone and not for causing a second fusion. a

Alternatively, the welding current may be terminated when the carriagehas completed a welding stroke and the current flow resumed at astress-relievinglevel when the carriage reverses. In either case, thefluid pressure cylinders are deenergized and the electrodes retracted inthe usual manner when said electrodes move off the work at the end oftheir annealing stroke, leftward as appearing in the drawing. 7 At thecompletion of the stress-relieving stroke, the motor 42 is stopped tolocate the planishing rolls over the left edge of the work parts 11 and12. The control 28 will then energize the fluid pressure cylinders 34and 38 to position the planishing rolls 29 and 31 against the left edgeof the work parts 11 and 12 to thereby compress said parts in a knownmanner to a thickness nearly equal to the thickness of one of the work.

parts 11 or 12. The carriage now moves (FIG. 3) andthe I planishingrollers will effectively cold roll the welded jointW to thereby coldwork same to increase the metal'strength The control 28 and carriage 19may then be recycled to the start position so that the process can berepeated.

If desired, the planishing rollers 29 and 31 may be secured to acarriage member which moves independently of the carriage 19. Themovement thereof can be, controlled by the control 28 so that alongitudinal movement thereof across the 28 will cause the source 27-toenergize the welding transthroughthe work parts held together underpressure by the roller electrodes 13 and 14. Simultaneously, the control28 will energize the motor 42 to cause a rightward movement the carriage19 and electrodes 13 and 14 as appearing in FIG. 1. As a result, theelectrodes 13 and 14 will roll on the work parts .11 and 12,respectively, along the elongated weld zone X to produce an elongatedweld seam W. lt will be noted that the planishing rollers 29 and 31 areheld away from the work parts 11 and 12 during the rightward movement ofcarriage 19.

When the carriage 19 has reached its rightwardmost limit, the motor 42is stopped and the welding electrodes 13 and 14 will in this embodimentbe positioned adjacent the right edge of the work parts 11 and 12 asappearing in FIG. 1. At this time the control 28 will modify the source27 to diminish the flow of welding current. The control 28 will thenreenergize the motor 42 in a reverse direction to cause a leftwardmovement of the carriage l9 and welding electrodes 13 and' 14. Thepressure supplied to the fluid pressure cylinders 18 and '23 can, inthis particular embodiment, be maintained constant so that theelectrodes 13 and 14 will be always urged against the work parts 11 and12 with a constant pressure. However, a

work parts 11 and 12 will occur at a desired rate of speed independentof the rate of speed of the welding electrodes 13 and 14. Thus,-theplanishing process may beaccurately controlled so that the resultantproduct will be smooth, unrippled and there will be a blend of one sideof the work part with the corresponding side of the other work part.

Although the foregoing detailed discussion relates only to the preferredembodiment utilizing one set of electrodes which move over the workpartstwice, under the broad concept of the invention the same operationcan be performed by two sets of electrodes, each of which makes one passover the work parts, first to weld a joint and second to stress relievethe welded joint.

Although the invention has been described with reference to a processwhich includes planishing the weld joint, the invention can also be usedto advantage in welding processes which do not include a planishing Istep. Conversely, if it is desired to effect a stress relieving of thejoint after the planishing step, regardless of whether or not such wasdone before planishing, same can be easily done merely by running thewelding electrodes at a low heat again over the weld zone.

While the particular method above described deals with the stressrelieving of a lapped seam weld, it will be understood that the broaderconcept of the invention will be also applicable to a butt joint whichmay be either are or resistance welded. In such case, a planishing stepwill be normally ciently smooth surface to effect good contact by thestress-relieving electrodes. I

Although a particular preferred embodiment of the invention has beendisclosed above for illustrative purposes, it will be understood thatvariations or modifications thereof which lie within the scope of theappended claims are fully contemplated.

lclaim: l. A method of seam welding, comprising the steps: placing workparts which are to be welded together between welding electrodes; I

bringing the welding electrodes into engagement with the work parts andsupplying welding energy thereto, simultaneously moving the weldingelectrodes and the work parts relative to each other to produce fusiontherebetween to thereby produce a welded joint;

thereafter moving electrodes over said welded joint and simultaneouslysupplying a stress-relieving energy to the electrodes to increase theductility of the welded joint by relieving the stresses therein; and

simultaneously with the foregoing controlling the first and secondelectrode movements so that the second movement will be faster than thefirst movement to limit the 7 heat supplied to the welded zone by thestress-relieving energy applied to the electrodes to a level which issufficient'to stress relieve the welded zone but insufficient forcausing a second fusion. v

2 The method of claim 1, including the step of planishing the weldedandstressed-relieved joint to cold work same to a thickness equal to thethickness of at least one of the work parts to increase the strength ofthe welded joint and to produce a welded joint having a desirableductility.

3. The method defined in claim 1, including the step of controlling thestress-relief energy to heat the welded joint to a temperature in therange of 800 to 1200 F.

4. The method defined in claim 1, including the step of preciselycontrolling the rate of the second movement so that the stress-relievingenergy will heat the welded joint to a temperature in the range of 800to 1200 F.

5. The method defined in claim 1, in which the welding electrodes andthe stress-relieving electrodes are the same electrodes.

6. The method defined in claim 5, in which the current which fiowsbetween said electrodes during the stress-relieving step is less thanthe current which flows between the electrodes during the welding step.

7. The process of claim 1, in which the work parts are lap welded.

8. The process of claim 1, in which the work parts are butt welded.

9. A method of seam welding, comprising the steps:

placing work parts which are to be welded together between weldingelectrodes;

bringing the welding electrodes into engagement with the work parts andsupplying welding energy thereto, simultaneously moving the weldingelectrodes and the work parts relative to each other to produce fusiontherebetween to thereby define awelcled joint;

thereafter moving electrodes over said welded joint and simultaneouslysupplying a stress-relieving energy to the electrodes to increase theductility of the welded joint by relieving the stresses therein; andplanishing the welded and stress-relieved joint to cold work same to athickness equal to the thickness of at least one

1. A method of seam welding, comprising the steps: placing work partswhich are to be welded together between welding electrodes; bringing thewelding electrodes into engagement with the work parts and supplyingwelding energy thereto, simultaneously moving the welding electrodes andthe work parts relative to each other to produce fusion therebetween tothereby produce a welded joint; thereafter moving electrodes over saidwelded joint and simultaneously supplying a stress-relieving energy tothe electrodes to increase the ductility of the welded joint byrelieving the stresses therein; and simultaneously with the foregoingcontrolling the first and second electrode movements so that the secondmovement will be faster than the first movement to limit the heatsupplied to the welded zone by the stress-relieving energy applied tothe electrodes to a level which is sufficient to stress relieve thewelded zone but insufficient for causing a second fusion.
 2. The methodof claim 1, including the step of planishing the welded andstressed-relieved joint to cold work same to a thickness equal to thethickness of at least one of the work parts to increase the strength ofthe welded joint and to produce a welded joint having a desirableductility.
 3. The method defined in claim 1, including the step ofcontrolling the stress-relief energy to heat the welded joint to atemperature in the range of 800 * to 1200* F.
 4. The method defined inclaim 1, including the step of precisely controlling the rate of thesecond movement so that the stress-relieving energy will heat the weldedjoint to a temperature in the range of 800* to 1200* F.
 5. The methoddefined in claim 1, in which the welding electrodes and thestress-relieving electrodes are the same electrodes.
 6. The methoddefined in claim 5, in which the current which flows between saidelectrodes during the stress-relieving step is less than the currentwhich flows between the electrodes during the welding step.
 7. Theprocess of claim 1, in wHich the work parts are lap welded.
 8. Theprocess of claim 1, in which the work parts are butt welded.
 9. A methodof seam welding, comprising the steps: placing work parts which are tobe welded together between welding electrodes; bringing the weldingelectrodes into engagement with the work parts and supplying weldingenergy thereto, simultaneously moving the welding electrodes and thework parts relative to each other to produce fusion therebetween tothereby define a welded joint; thereafter moving electrodes over saidwelded joint and simultaneously supplying a stress-relieving energy tothe electrodes to increase the ductility of the welded joint byrelieving the stresses therein; and planishing the welded andstress-relieved joint to cold work same to a thickness equal to thethickness of at least one of the work parts to increase the strength ofthe welded joint and to produce a welded joint having a desirableductility.
 10. The method of claim 9, in which the planishing stepfollows the stress-relieving step.
 11. The method of claim 9, in whichthe planishing step precedes the stress-relieving step.